The breakdown of a semi-tractor which is hauling a cargo trailer while en route or at a location away from a home station having service facilities, obviously an inconvenience, is also a costly interruption in the operating routine of a trucking fleet.
Typically in the event of a breakdown, a tow truck and service person and a substitute semi-tractor (with driver) are dispatched to the site. The substitute semi-tractor is hooked up to the cargo trailer to allow completion of the intended trip and the disabled semi-tractor is towed to a service location and returns the original (or substitute) driver. Various tow trucks, tow lifts and other types of towing apparatus for semi-tractors have been described in U.S. Pat. Nos.: 3,715,042, 4,149,643, 4,316,617, 4,152,006, 4,047,733, 3,649,048.
U.S. Pat. No. 4,149,643, entitled "Truck Tow Lift" and issued on Apr. 17, 1979, describes a fifth-wheel connection between a first towing semi-tractor and a second (presumably disabled) towed semi-tractor. In this apparatus, a lifting winch mechanism is mounted on a rectangular frame which includes SAE king pins at each end thereof for connection to the fifth wheels respectively of the first towing semi-tractor and the second towed semi-tractor. Rigidizing members are included in the frame; the lifting winch mechanism lifts and supports the rear wheels of the towed semi-tractor from ground contact for towing by the first semi-tractor.